Abstract

The pentacyclic triterpenoids from birch (Betula platyphylla suk) have broad pharmacological activities and can be potentially used for the development of anti-cancer and anti-AIDS drugs. In this study, we explored the effects of spraying 3-year old white birch with different concentration of methyl jasmonate (MeJA) and salicylic acid (SA) on the expression of key genes in triterpenoid biosynthesis pathways and on the accumulation and physiological characteristics of triterpenoids in birch saplings. The results show that, spraying different concentration of MeJA and SA could obviously promote accumulation of total triterpenoids in 3-year old white birch. The triterpenoid content in the stem bark was significantly increased after 1d of treatment with 1 mmol·L-1 MeJA (MJ2) and after 14 d of treatment with 5 mmol·L-1 SA(SA1), triterpenoid contents of MJ2 and SA1 reaching 81.86 mg/g and 91.40 mg/g, increased by 46.11% and by 45.07% compare control(CK), respectively. In addition, MeJA and SA treatment increased the contents of chlorophyll a and b, antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and photosynthetic performance, and affected the content of soluble sugar and soluble protein in birch leaf. Fluorescence quantitative polymerase chain reaction (qPCR) results showed that MeJA and SA treatment deferentially enhanced the expression of key genes farnesyl diphosphate synthase (FPS), cycloartenol synthase
(BPX and BPX2), lupeol synthase (BPW) and beta-amyrin synthase (BPY) in triterpenoid synthesis pathway in birch bark and leaves. The results showed that MeJA and SA induced triterpenoid synthesis of birch plant is closely related with not only the expression of key genes of triterpenoid synthesis pathway but also photosynthesis, anti-stress response and physiological indexes, suggesting regulation of triterpenoid synthesis of birch by MeJA and SA may involve in more complex mechanisms at physiological and molecular level.